It is already known (U.S. Pat. No. 2,133,005) to give the cutting edge of a stripping knife an approximately semicircular shape in order that an insulation layer of a conductor having circular cross-section may be surrounded to the greatest possible extent and cut through by two such co-operating cutting knives. The top line of the cutting edge is mostly located adjacent one surface of a metal plate which defines the body of the cutting knife and which has a certain thickness, so that a sloping chamfer extends between the two limiting surfaces and subtends an acute angle with the first mentioned limiting surface.
It is also known (U.S. Pat. No. 3,336,666 or U.K. patent No. 1,577,947) to provide, in connection with a stripping knife having a straight cutting edge, a positioning device for the conductor to be stripped. The positioning device is stationary relative to the cutting edge and is defined by a tapering, e.g. V-shaped or semicircular recess into which the conductor is forced.
The positioning devices known up to now have the disadvantage that they, in order to allow for the cutting knives to penetrate into the insulation cover to a given depth, only insufficiently retain the conductor, particularly at the instant of first contact between the conductor and the cutting edge.